Coputer to Lab power supply conversion

Is that an old 90 watt PCXT power supply???? Those needed a load similar to an ST506 hard drive or an amp or so on the 12 volt line. In any case, you don't say what the current capability is of the 12 volt output. 90 watts is likely the total supply capability inclusive of all its outputs.

YOu need to try it.. I would say most likely it'll work. Some people put a 12 incandescent lamp on the circuit so that it can be used for both load and indication!

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Sorry, i'm not sure what kind of ower supply it is, all i can tell you is the model number sfx-1209f. and yes, 90 watts is the overall out put. 1.5 amps are availble on the 12 volt channel. here is another though, since i only plan on using the 12v channel would it be a better idea to load the 5 volt channel? Thinking out loud.... I'll probablly go with jamies ide and just try it. obviously I'll have to bost the resistance since less current is going to be pulled at 5v. perhaps some led's? i'll ned a few of em to pull enough amperage...

As a hobbyist, you should build your first power supply! At 1.5A, you can easily get this with a either a linear regulator or you can opt for a switching regulator. In either case, the parts count is low. A quick google search should get you some part numbers from which to start.

If you still wish to use the computer power supply, load it with an incandescent bulb. A 6 volt bulb on the 5 volt output is not a problem.

Sounds great, there are just a few problems. I'm 17 and my parents are not hobbyist. Anything that plugs into the wall terrifies them. I'm already going to have to plug this "proffessionaly" made power supply into a surge protector so I have a remote switch of sorts. The second I opened the case to get at the PCB my parents swore they'd never let me plug it in. It's funny really. I'd feel so much safer plugging in my own creation than some mass produced peice of junk from China, which they do on a daily basis.

sounds good. I'll pick one up from radio shack or something. Thanks for the help!

Hi ngbud,

I have a computer power supply maximum 185 Watts load. It is a switching power supply which needs to have a load to stabilize before start up. I have read that the load should be roughly a minimum 5% of total capacity. [In your case... 90W=D75% =3D 4.5W]

If that is applied to the 12v output it would be 0.375 Amp and for 5v output it would be 0.9 Amp. I don't know if that is correct, you should check my figures, I have ADHD and am not very intelligent.

The load resistance I use on my 185W power supply is two 6v incandescent light bulbs in parallel connected to the 5v output. I arrived at that amount by watching the PS fan after adding the various loads, as explained in the instructions/guide below:

This guide, which I found online years ago, is for my particular power supply, but it can be used to get an idea of how to hook up your PS resistors..

1) Make sure the on/off switch is off.

2) If there is a switch for selecting either U.S. Standard 115 volts AC or European 230 volts AC make sure it is set accordingly.

3) Connect a load resistor from +5V to ground or from +12V to ground.

4) While looking at the fan turn on the power supply. If everything is hooked up correctly the fan should spin and run at a constant speed. If the fan doesn't turn on or it turns on briefly and then shuts off there is something wrong, check to see if the load resistor is properly connected. If the fan pulses continuously, turning on, off, on, off then it is almost working, but the load resistor needs to be smaller.

I found that using incandescent bulbs as the resistors worked well. I didn't have to calculate resistance or worry about power-heat- dissipation values. The bulbs I used were like the 12v courtesy lamps found in automobiles, except they were 6v. Circuit designs found in old electronics~electricity experimenter books frequently use incandescent bulbs as resistors and indicators.

I'm sorry I don't have a reference URL for the instructions above. I only have author and date: Max Davis 10/00.

My Power Supply: Compaq # 172417-002 [172432-001] Purchased from

Catalog # PS-185

I am not an expert in electronics. Please check my information and calculations before applying them to your situation.

insula

;-)

.allelectronics.com/ Catalog # PS-185

Thanks Nick. BTW, good name ;-). There was a lot of great information there. I'm going to see if i can find some 6v bulbs this week and try it out.

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Hi Jerry,

you posted url:

I had trouble accessing that page with my antiquated webtv.net technology, I eventually got it to work, however I also found an alternate page that worked well with my system.

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